Toll-service trunking system



July 17, 1928.

J. WICKS TOLL SERVICE TRUNKING SYSTEM 3 Sweets-Sheet I AllAAlAAlA mien UI' Jul-m hflcks Ju1 17,192s. 7' 1,677,876

' J. WICKS TOLL SERVICE TRUNKING SYSTEI John Jnfzzks July 17, 1928. 7 1,677,876

TOLL SERVICE TRUNKING SYSTEM flripinal mm 16 1923 J. WICKS 1 haefis-Sheet 3 Patented July 17, 1928 unit-Ea STATES PATENT OFFICE.

JOHN WICKS, OF OAK .PARK,.ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO I MJATICZEIJEGTRIC. INCL, 01Ev CHICAGO, ILLINOIS, A CORPORATION OF.DELA\KFARE;.

TOLL-SERVICE TRUNKING SYSTEM.

Application. filed June 16, 1923, Serial No..645,714. Renewed June 18, 1927.

The present invention relates in general to telephone systems,.but is particularly concornedv with certain conditions which arise when aportion of the ofices of a manual sys tem are. changed over to automatic. When thisds done some specialmeans must be provided .to enable the operators at the toll ofiice to complete incoming toll connections to subscribers of theaut-omatic oflices. In some instances this has been accomplished by providingsuch toll operators with the proper impulse sending. apparatus, which method is satisfactory under certain conditions. Local conditions however are sometimes such that the added cost of installing this apparatus at. each tolloperators.position is excessive, or the toll operators are already taxed to their capacity and therefore would not be able to giveefi'cient and speedy service were this burdenadded. The object of the invention. thereioreis to provide means whereby it is unnecessary to provide the toll operators with. impulse sending equipment, but instead when a callis received for a subscriber. located in an. automatic oflice the operator. repeats the desired number to a B operator in thatoiiice, the B operator having the proper impulse sending apparatus to complete the connection.

Another object lies in the provision of novel.su-penvisory control circuits, which enable the tolloperator to have full supervision of. the callaifter the B operator has transmittedi the impulses required to obtain the wanted subscriber.

Referringto. the drawings, Fig. 1 shows an incoming toll line X, an outgoing trunk Y, and a cord. circuit for linking the two together;

showsa B operators equipment for settingup an automatic switch train, and a Selector switchD.

Fig. 3 shows a final or connector switch, a line switch C and a called line A. i

The cord. circuit. 0, Fig. 1 is of a type commonly used by toll operators in manual systems for. answering incoming calls aswell as for completing toll connections.

The group of relays in the outgoing trunk Y shown. at the right of Fig. 1, together with the two interrupter devices I and I are for controlling a supervisory signal as will be. fully described-subsequently.

The B operators calling device C1 D1 (Fig. 2) is of the type in common use at the substations of modern automatic telephone systems,

The selector D (Fig. 2) in the automatic oiiice is mechanically of the well known Strowger type andaccordingly has its bank contacts arranged in horizontal rows or levels. The circuit or the said selector is shown complete and will be fully described hereinafter.

The connector H, Fig. 3 is ofthe well known Strowger, vertical and rotary type which'may be seized by means of a selector such asthe selector D inorder to. complete conections to calledstations such as the one shown at A.

The apparatus having been described in general, a detailed description will now be. given. For this purpose it .is assumed that" the toll operator at the toll oifi ce receives a. call over the toll: line X, Fig. 1. It is' further assumed that thedesired station is station A- (Fig. When a call comes in over the toll'line X" the ring down relay 8'is operated causingthe lamp L to glow. The operator upon'observ ing the lighted'con'dition of lampfLv responds by inserting the plug Poi her cord O'into the answering jack J. This results in the operation of cut-oil relay 4' in. series with. the sleeve relay 5. Relay 4 in operating opens the initial operating and locking circuits of ring down relay 3 and closes a cir cuit for the visual busy signalland all'multi ple visuals at other positions.

The operation of relay 5 closes a point in" the circuit of lamp 6 and in the locking cir'-' cuit of ring up relay 7 There is no bat-'- tery normally flowing on trunk line X and therefore relay 7 will not be operated unless the operator in the distant ofiice sends ringing current over the trunk.

As soon as the operator plugs into the toll line she throws her listening key, and after" ascertaining that the station desired is sta-' tion A of an. automatic oflice, operates the: button 7 connectmg her order wire with the B operator of that oflice. The toll operator now repeats the desired number to the B" operator at the automatic office. The B operator selects an idle outgoing-trunk as indicated by the extinguished lamp, such as in an automatic office. I

the lamp 8, operates her calling device key K and assigns this idle trunk Y to the toll operator.

The B operator in operating her calling device key completed a circuit for the line relay 21 of selector D as follows: from rounded elf normal springs 48, lower winding of line relay 21, armature 47 of relay 25 and its resting contact, springs 49 and 50 of the key K, through the calling device C. D., springs 51 and 52 of the key K, armature 46 and its resting contact, and the upper winding of line relay 21 to battery.

Line relay 21 energizes and completes a circuit for slow release relay 22 which also energizes. Relay 22 111 operating, at its upper armature grounds the release trunk 36 causing the lamp 8'at the B operators position to glow, thereby indicating the busy condition of the trunk. Relay 22 also prepares the usual operating circuit for the series relay 23 and vertical magnet 28.

Referring now for a moment to Fig. 1,

it will be seen that when the toll operator inserts the plug P into the jack J of the assigned trunk Y a bridge is completed across this trunk, extending from trunk conductor 18, springs controlled by armature 9 of relay 10, upper armature and working contact of relay 11, windings of relays 12, 13 and 14, and through contacts controlled by armature 16 of relay 10 to conductor 19.

:It will be evident that none of these relays are operative at this time because the trunk is open at springs 49 and 52 while the calling device key K is in operated position.

Now returning to the operation of the selector switch D, the B operator will now operate the calling device C. D. In accord ance with the telephone number of the sub-' station A. When the calling device dial is operated in accordance with the first digit of the number a series of interruptions is produced in the circuit of the line relay 21. Re-

sponsive to these interruptions in its circuit, relay 21 deenergizes momentarily and at each deenergization sends a current impulse through the slow acting series relay 23 and "the vertical magnet 28 to battery. By the operation of the vertical magnet the shaft is raised step by step until the wipers 33 to 35, inclusive, stand opposite the horizontal level of bank contacts which are terminals of "trunk lines leading to the desired group of attracted during the vertical operation of the switch, and closes a circuit for the stepping relay 24. The stepping relay 24 is therefore energized, and when the off normal springs are shifted at the first upward movement of the switch shaft, establishes a locking circuit for itself by way of the off normal springs 38. At the end of the vertiits working contact and the winding of mag:

net 27 to battery. The rotary magnet is accordingly energized and advances the wipers 33 to 35, inclusive, into engagement with the first set of bank contacts in the level opposite which they were raised. Near the end of its stroke the rotary magnet breaks the circuit of stepping relay 24, which is accordingly deenergized to open the circuit of the rotary magnet. Both the steppng relay 24 and the rotary magnet 27 having deenergized, the operation now depends upon whether the test contact with which the test wiper 34 is in engagement is busy or is not busy. If this test contact is busy it will have a ground potential upon it and a cirunit will be established which extends by way of the said test wiper, armature 45 and its resting contact, off normal springs 38, interrupter springs 41 and the winding of stepping relay 24 to battery. By current flow over the above circuit the stepping relay 24 is again energized and again closes the circuit of the rotary magnet 27 which in turn operates to advance the switch wipersinto engagement with the next set of bank contacts. This operation continues as long as the test wiper 34 continues to engage grounded contacts. As soon as the first nongrounded test contact is reached, which we will assume to be the contact 43 associated with the trunk line comprising conductors 60 to 63, the stepping relay 24 will not again be energized, and the rotary movement of the switch will cease. The switching relay 25, which heretofore has been short circuited is now energized over the following circuit: grounded release conductor 36, winding of relay 25, off normal springs 38, interrupter springs 41' and the winding of relay 24 to battery. Relay 25 is of such high resistance that the stepping relay 24 is not energized at this time. Upon energizing relay 25 connects the test wiper 34 to the grounded conductor 36 in order to make the multiples of the test contact 43 busy to otherswitches, opens a point in the circuit of the release magnet 26 at armature 29, and at armatures 46 and 47 disconnects the line relay 21 from in bridge of the trunk line Y and substitutes lit) the conductors 60 and 62 across which are c bridged the windings of line relay 63 of the connector H. Line relay 63 is energized and completes a c1rcu1t for slow acting release relay 64. Upon energizing, relay 64 conis prevented-1 from releasing at this time; ands. the lampzS continues toglow. Relayfietzalso. at its armature 82 prepares aci-rcuifiior'the. series relay and vertical magnet 72 in. the usual-manner.

The B operator may callingdevice C. D. for the next digit ofthe:

desiredinumber; By this operation. a. series of lnterruptlons lSPIOClUCQClLlII the circuitiori the line relay 63. At. each deenergization,

animpulse of currenttis sent over a circuit extending from grounded"armature.of relay 63 and its resting contact, armature 82 and. its: working contact, oil normal. springs 83 and? 85, and. the windings of: relay 65;, and:

vertical. magnet. 72 to'- battery: The above:

is the. circuit over which the first impulse to the vertical. magnet. isxsent.v Upon the;

first vertical step 01; the switch, the OE. nor"- -mal' springs are shifted: and the. remaining impulsesvto: the magnet traverse anew circuit which is the same. as the one. above traced except. that it. includes the oft nor malisprings- 83 andr84 and armature ofrelay 65' and its working contact, relay 65. being now in an operated position. The verti cal magnet 72. operates to: raise the switch wipers 98 to 100 inclusive, step by step until: they are placed opposite the; level of bank contacts" in which is located the. contact set associated with the line of substation A. The. slow acting-relay 65 is energized in series with the vertical magnet 72. and maintains its armature attracted throughout thexvertical movement of the switch, and at the terminatlon thereof deenergizes, transferring the operating circuit to the rotarymagnet 70.

The B operator may now dial "the next and final digit of the desired number. As before a series of interruptions is produced in the circuit of relay 63 resulting in impulses of current being sent to the rotary magnet. over a circuit extending from'grounded' er mature and resting contact of relay 63, ar-

mature and its working; contact, ofi normal springs 83 and 8 1-, armature of relay 65 and its resting contact, resting contact of armature 86. and the said armature, armatu-re and its resting contact, windingsof slow rela-y68 and rotary magnet in multiple to battery. In response to these 1111* pulses the rotary magnet 70'operatesto ro tate the wipers 98, 99 and 10@ into engage- .mentwith the particular setv of bank contacts in which the line of substation A/termina-tes, these contacts being the contacts indicated in the drawing by the reference numerals 86, 8? and 88.

The B operator having completed dialling the desired number she will now restore the key Kito normal substituting the relays 12,

13" and' 1 1 in bridge of trunk conductors 18 and 19 forrthe calling device'Cl. D. The call ;.is now completed so :tar as the Bl operator now operate: the.

isJ-concernedl.thetlamp: 8a-howeuerznemaining lightedato: indicate-to theiB cperatonthaathis ole; callin device manuallv' connected and:

disconnected from 1116 trunk bynmeans of; a key. In: actual. practice. however, regular, operatorsvinipulse sending; equipment; wilt usually: be used, such for: instance as that.

shown in co-pending. application of Martin;

L.. Nelson Serial No. 492,9Z6, filed August.

As a-- result-10f. relays. 12;, 13 and: 14:; being bridgedi across the outgoingtrunks, anyone 01% three conditions. may: be indicated 1 by the. supervisory lamp 26) in theA; operators cord..

It the selector D failed tofindrim idletrlmk only relay 113 will be; energized? and lamp, 201

will flash; at the rate of 120 flashes per.

an idletrunk and the connection was. com pleted to a busy called line, relays13 and 1 1-: will: bothbe. energized: and; lamp 20: will.

It will first be assumed that all trunks,

in the elected groupwere busy. This being the case magnet 27 of the selectorv D is there- 'fore operated to move. the wipers one stepbeyond'the last trunk. of the. group. When this occursthe rotary off normal cam. operates springs 48.- and 48, and causes the minute It the selector succeeded-2m:findingground through relay 2.0. to be substituted for direct ground, and'lcauses also. thecilrcuit of relay 25 to be opened" at. contacts 4'8 to; prevent. thee'nergi'zation of relay 25, atthis time.

The. relay 20! energizes series with relay 21,,and in. operating its armaturecnts initshigh resistance. winding: The. Bop,- erator of course does not know; that all the trunks. are busy and therefbre. the 0.0mplete impulse series for operating, thev connector'H will be transmitted; In this case. these impulses willv again operate the. line. relay 21 causing impulses to be.v again transmitted ta-the vertical magnet. 28, but; the vertical. magnet: will not client the movement of the switch wipers. as they have. ale ready been rotated. (This unnecessary operation Oif the vertical magnet. may be east.- ily' avoided by placing rotary ofli normal springs the vertical. magnet circuit. if desired.) It will be. seen that. each time the. circuit of relay 21 is. interrupted. the high. resistance. winding of relay 20 will be. shorts ed so, that the reenergization of. relay 21. is

always assured. This is essential as it will be seen that were the high resistance permanently cut in, the line relay might fail to again energize and the selector would be released, and the A operator would receive a false signal. When the impulses have all been transmitted and the B operator iestores her key K the high resistance of re lay 20- being in series with theline relay 21 and relays 12, 13 and 14, marginal relay 14: and polarized relay 12 (relay 12 not being actuated until the current flow has been reversed) will not be operated. Relay 13 however pulls up and completes a circuit from battery, resting contact of armature 9 and the said armature, tip side of jack J, tip of plug P, upper springs of key K, up per right hand winding of repeating coil R, winding of relay 15, lower right hand winding of repeating coil It, lower springs of key K, sleeve of plug P, sleeveside of jack J, armature 16 and its resting contact, resistance 17, working contact and armature of relay 13, armature of relay 14 and its resting contact and the interrupter I to ground. The circuit of supervisory relay 15 in this instance has its circuit broken 120 times per minute causing the lamp to be flashed accordingly. The A operator upon noting the rate at which the lamp is flashing will know that she cannot complete the call at this time and will remove the plug P from jack J. This first results in the deenergization of sleeve and trunk relays 11, 10 and line relay 21 of'repeater 1), followed by the release of relay 22. The retraction of armature 31 of relay 22 completes a cir cuit for the release magnet 26. This circuit extends from grounded resting contact of armature 29 and the same armature, armature 30 and its resting contact, armature 31 and its resting contact, ofi normal springs 25 and the release magnet 26 to battery.

The operator before withdrawing plug P from jack J operates her listening key K and informs the calling party that the call cannotbe completed at this time, or she may again operate key 7 and again attempt to complete the call.

Assuming that the operator immediately calls again, and further that this time the called line is busy. After the final series of impulses have been. transmitted to the rotary magnet 70, and before slow relay 68 deenergizes, a circuit is completed for the relay 67, from busy or grounded test contact 87, wiper 99, armature 88 and its working contact and the winding of relay 67 to battery. The relay 67 operates, and at its armature 102 prepares a locking circuit for itself which is closed when the relay 68 deenergizes a moment later. This locking circuit extends from the grounded test contact 87, wiper 99, armature 88 and its resting contact, armature 102 and its working contact and the winding of relay .67 to battery. At

its armature 86 it opens the operating circuit of relay 68 and rotary magnet and at armature 101 opens a pointin the operating the line becomes idle ground will be re moved from test contact 87 and battery substituted. When this occurs the relay 67 after a slight delay deenergizes and at armature 101 completes a circuit for'relay 69, which may be traced as follows: from, grounded working contact of armature 81 and the said armature, armature 101 and its resting contact,-upper winding of relay 69,

wiper 99, test contact 87, winding of relay 7 90, interrupter contacts and winding of magnet 91 to battery.

Upon the closure of the above circuit relays 69 and 90 are energized in series, and the latter relay is operated to disconnect the line conductors 92 and 93 from their normal connections in the line switch G. Relay 90 is not completely operated because of the fact that the line relay of the line switch has not been energized and does not connect the line conductors with the wipers of the switch. In the connector H, the relay 69 upon energizing opens the circuit of the rotary magnet 70 at armature 94:, establishes a locking circuit for itself at armature 103, connects ground to the test wiper 99 at armature 95, thus closing the circuit of relay 90 over a new path excluding the upper winding of relay 69 which was formerly included in the circuit, and at armatures 96 and 97 closes the signalling circuit thru to the line wipers 98 and 100. This circuit may be traced from interrupted generator Gen, lower resting contact and armature of ring cutoff relay 66, armature 97 and its working contact, wiper 1.00, bank contact 88, conductor 93 to and thru the called line signalling apparatus, conductor 92, contact 86, wiper 98, Working contact and armature 96, upper armature and resting contact of cut-off relay 66 and the upper winding of said relay to battery.

Relay 69 in operating at its armatures 75 and 76 also reverses the current flow in the calling line conductors. Referring to Fig. 1 the current flow being reversed polarized relay 12 now operates closing a circuit for relay 10, which operates and locks itself up independent of relay 12 and at its armatures 9 and 16 disconnects the relays 12 13 and let from bridge of the line and .at the same .armatures and their working contacts substitutes the supervisory relay 1.5. relay energizes causing the lamp 20 to burn steadily. This signal informsthe operator thatthecalled line is now idle and is being signalled.

VJ hen the called subscriberresponds the current'fiow th-ru the upper winding of ring cut-off relay 6,6 is suificiently increased to cause it to operate to disconnect the ringing current and to substitute the back bridge relay 73 in bridge of the called line. This relay operates and at its armatures 79 and 7 7 disconnects the line relay from thecalling line conductors and maintains it energized in -.a local circuit. The removal ofbattery from the calling line conductorscauses the supervisory ,relay 15 in the cord circuit Oto deenergize to extinguish, the lamp 20, notifying the operator that the called subscriber has responded. Theoperator may now operate her listening key to further supervise the call :as desired.

Had theline been idleat the time that it was-seized the relay67 would of coursenothave :been'operated and immediately upon the slow relay '68 restoring, the relay 69 would have operated to [start the ringing and to reverse :the current flow in the calling line in the manner above described.

After the conversation has been completed the subscribersreplace their receivers. Upon the subscriber A replacing his receiver the "back bridge relay 7 3 deenergizes and again connects line relay 63 in bridge of ithe'line. This causes the supervisory reday to again energize causing the'lamp 20 to glow toinformthe A operatorthat theconversation has been completed. The replacement of the receiverat the calling substation causes the usualsupervisory signal 'at the operators position at that-exchange to be operated in well known manner.

The-.operaor :maynow withdraw the plugs FPand P from their respective jacks. The removal of plug P from jack IJ removesithe bridge from trunk conductors 18 and 19 causing line and release relays 63-and 64 to deenergize to complete a circuit for release magnet .7'1,:to'restore'theswitch H toinormal.

Relaybei in retractingits armature .78 also removes ground from switching relay 25 of 'the selector D, and fromthe lamp .8 at the B operators position. Relay 25 in restoring, at its armature 29 completes the pre- -viouslyw described :circuit .for release magnet 26 causing releaseotthe selector 1). All apparatus is now at normal and in :readiness to be :seized for any subsequentcalls, lamp 8 being extinguished, again indicating the idle conditionofitheztrunk llI16'tOith6 B operator. v

What-isclaimed isz ;1. In a telephone system, a manual cffice This.

and an automatic oflice interconnected ,by trunk lines, an .operatcrgs cord circuit at the manual ,otfice for completing calls ,to subscribers of either .ofiice,-mean s for providing order wire service between said ofi ices-to' permit an operator at the .manual ofiice to repeat numbers of subscribers in the automatic .oflice .to an operator thereat'and to permit such operator to assign one .of said means ;fOI'.1SQlZlI1g said trunk line .at the manual .ofiiee, means at theautomatic joflice for controlling said automatic switch tosev.lect a particular group. of trunk lines to hunt for an idle trunk .in that group,,,a

group of controlling, relays in the ,manual end. of said first trunk, and means in sa d automatic switch effective when all of .a trunk grouparebusyfor preventing the ,operation of .a particular one of said relays while permitting the operation of another.

of said relays to. controlla supervisory signal at the manual. oflice 3 in. a distinctive .inanner.

3. In a-telephonesystem,,a:trunk linehaV- ing one end terminating'in a jack andlthe other end terminating in .an .automatic switch; means at an intermediate :point ,in

said .trunk *line fordisconnecting the .por

tion of the trunk terminating in the jack and for controlling the movement (of said switch over the other portion, other automatic-switchesaccessible to said first switch and-having access to calledlines, themeans ,for controlling the first .switchalso being adapted to control saidother sWitcl1eS,, a cord circuit for extendingconnections to said trunk line, asignal in said .cord, .and means insaid trunk for variably {operating said signal (to inform .anoperator whether- {the line has beenseized orwnotzand the con- 1dition of the. called line. if seized.

14. In. combination, a cord. c rcuit, .a trunk line, a series of automatic switches and a called line, means associated with saidetrunk ,line for transmitting impulses ,for position .ing said automatic switches to setup a. connection with said called line, a signal linsaid cord .circuit, and means in said trunkefied .tive in a manner dependentupon v,thFrIulIm ber of automatic switches operated or upon the condition-of thecalled line :whenseized number-of switches operated and to indicate Whether the called line is busy or idle in case all said switches are operated.

5. In a telephone system, an 7 operators switchboard in a manual o'lfice, an operators switchboard in an automatic office, a trunk line connecting said switchboards and also having a branch terminating in an automatic switch in said automatic ofiice, other automatic switches, auxiliary means of communication between said switchboards for permitting an operator at the manual ofiice to repeat called numbers to an operator in the automatic oiiice, 'means at the switchboard of the latter oiiice for controlling said automatic switches to extend connections to 7 called lines, a supervisory signal at the manual ofiice, and means in said trunk for operating said signal in two distinctive ways upon failure of the call and operable in still another way if the call is successful.

6. In atelephone system, a toll oi'iice, an automatic exchange, an interconnecting trunk line terminating in a selector at the automatic exchange, groups of connectors accessible to said selector, means at the auto matic exchange for operating said selector to select a group of connectors and an idle connector in the group and for then operating the selected connector to connect with a called line, a signal at the toll o'liice, and means including three relays in a bridge of said trunk for operating said signal in three different ways depending on whether the desired group of connectors is busy, and on whether the desired called line is busy or idle. 7. In a telephone system, a toll ofiice, an automatic exchange, an

automatic exchange, groups of connectors accessible to said. selector, means at the automatic exchange for operating said selector to select a groupof connectors and an idle connector in the group and for then operating the selected connector to connect with a called line, a signal at the toll office, said signal comprising a lamp, a relay for flashing said lamp if the selector fails to find an idle trunk line in the selected group, means including a marginal relay in series with said first relay for flashing said'lamp in a diflerent way if the called line is busy, and means for lighting thelamp steadily if the called line is idle.

' 8. In a telephone system,.a trunk line extending from a toll oilice to an automatic office, a signal, a supervisory relay controlling said signal, three relays bridged across said trunk line, a steady energizing circuit for the supervisory relay controlled by one of said three relays, a flashing circuit for said supervisory relay controlled by another interconnecting trunk hne terminating in selector at the of said three relays, a different flashing circuit for said supervisory relay controlled by the other of said three relays, and means 1n the automatic oliice for controllin said three 'said interrupters with the other of said sections, and a polar relay also included in said bridge for controlling the connecting or SfiKl'SGClZlOIlS together.

11. In a telephone system, a selector hav- 7 ing a line relay, a circuit for said relay, a second relay having two windings, means actuated in the operation of said selector for including one winding of said second relay in said circuit, and contacts on said second relay for including its second winda ing in said circuit also.

12, In a telephone system, a trunk-hunting switch, two energized relays, a resistance unit, and contacts operated responsive to a movementof said switch beyond its trunking range for inserting said unit in series with said relays whereby one relay falls back and the other remains operate 13. In a telephone system, a trunk huntswitchhaving a line conductor, a line relay having a winding connected to said conductor a resistance unit having a resistance substantially higher than the resistance of said winding, and contacts operated responsive to a movement of said switch beyond its trunking range for inserting said unit in series with said winding.

14:. In a connector switch, a line relay and means controlled thereby for operating the switch to connect with a called line, incoming trunk conductors terminating in said relay, a switching relay operated when the called line is connected with to reverse said conductors with respect to theline relay windings, and a battery feed relay in said connector opera-ted when the called party answ-ersfor disconnecting said conductors from said line relay. 1

15. In a connector switch, a line relay and means controlled thereby for operating the switch to connect with a called line, incoming trunk conductors terminating in said relay, a switching relay operated when the called line is connected with to reverse said conductors with respect to the line relay .windings, a battery feed relay in said connector operated when the called party anizo 'swers for disconnecting said conductors fronrsaid line relay, and contacts on said battery teed relay for closing a local circuit to maintain said line relay energized.

16. In a connector switch, a line relay and means controlled thereby for operating the switch to'connect with a called line, incoming trunk conductors over which said line relay is controlled, a relay in said connector operated when the called line is connected with to reverse the direction of current flow in said conductors, and another relay in said connector controlled over the called line to "stop'theflow of current in said conductors.

17. In'a telephone system, a trunk line having one end terminating in a jack and the other end terminating in an automatic switch, means at an intermediate point in said trunk lineior controlling the movement of said switch "over the trunk line, other automatic switches accessible to said first switch and having access to called lines,'said last mentioned switches being controlled by way of said first mentioned switch, a cord circuit for extending connections to said trunk line, a signal in said cord circuit, and means in said trunk for variably operating said signal to indicate whether a called line has been seized and to indicate the condition of the line if it has been seized.

18. In a telephone system, a trunk line having one end terminating in a jack and the other end terminating in an automatic switch, means at an intermediate point in said trunk line for transmitting groups of digit impulses over the trunk line to extend a connection to a desired station, a cord circuit for extending connections to said trunk line, a signal in said cord, and means in said trunk for variably operating said signal to indicate to an operator which was the last group of digit impulses to be effective to extend the connection from the trunk line.

19. In a connector switch, a line relay, means controlled thereby for operating the switch to connect with a called line, incoming trunk conductors over which said line relay is controlled, said relay applying a potential to said conductors, a relay in said connector operated when the called line is connected with to reverse the direction or the potential applied to said conductors, and means operated when the called party answers for removing said potential from said conductors. I

20. In a telephone system, a selector having a line relay, means for establishing a circuit for said line relay, two resistors, means actuated in the operation of the selector for including one of said resistors in said circuit, and means effective responsive to the insertion of said one resistor in said circuit for including the second resistor in series with the first resistor.

21. In a telephone system, the combina- -t-ion"with a telephone line, 01" an automatic switch, groups of trunk lines terminating at said switch, an operators posltion, a s gnal lam) thereat means for oceratin said switch to select a desired group of trunks, means 1n said switch automatically BfiQCtIVG to select an idle trunk in the selected group of trunks, and for extending the line over the selected trunk means effective if the switch fails to find an idle'trunlr for inserting a resistor in series with the line, a marginal relay in series with the line, said marsaid resistor, means controlled by the mar-'" ginal relay being inoperative in series with ginal relay for flashing the lamp in a pretrunk in the selected group for flashing said lamp in another manner.

22. In a telephone system, a line terminating in a selector'including a line relay, said selector having access to a plurality of groups of trunks each of which trunks terminates in an automatic switch, means for transmitting digit impulses to the line relay of the selector to cause the selector to select a desired group of trunks, means for automatically operating the selector to select an idle trunk in the selected group, means effective responsive to the selector failing to find an idle trunk for inserting a resistor in series with the line relay, means responsive to subsequent digit impulses transmitted to the line relay for periodically removing and reinserting said resistor in said circuit, said resistor being excluded from the circuit when the line relay is released by the digit impulses and included in the circuit when the line relay is operated by the digit impulses, whereby the periodic operation of the line relay is assured, and signalling means controlled by said resistor for indicating whether an idle trunk has been found.

23. In a telephone system, a manual exchange, an automatic exchange, a trunk connecting the two exchanges and terminating ina selector at the second exchange, said selector having access to groups of trunks,

a cord at the first exchange for extending'a connection to said first named trunk, means at the second exchange for transmitting digit impulses to the'selector for operating the selector to select a desired group of trunks, said selector being automatioally'operable to select an idle trunk in the selected group, a marginal relay and a supervisory signal at the first exchange, and means at the second exchange for controlling the marginal relay to operate the signal to indicate whether an idle trunk in the selected group of trunks has been found.

24. In a toll switching system, a toll operators position, an incoming toll trunk terminating at said position, automatic switches accessible from another operators position, order wire service between the two positions, a trunk connecting the two positions, dialling equipment at the second operators position for extending a. connection from the last mentioned trunk, and a toll cord circuit at the first mentioned position for connecting the incoming toll trunk with the last mentioned trunk.

25. In a telephone system, a toll board at which incoming calls are received, an automatic exchange, a toll switching train comprising automatic toll switches at said exchange, a dialling operators switchboard, a trunk extending from said toll board to said automatic exchange, means at said switchboard whereby the operator thereat may control the operation of said automatic toll switches over said trunk in accordance with the number of a called line as communicated to her by the toll operator at the toll board, and means at said t-oll board whereby the toll operator may complete the toll call over said trunk.

26. In a telephone system, an exchange, a toll switchboard at said exchange, a special dialling operators switchboard, an automatic exchange, trunks extending from said toll switchboard to said automatic exchange, automatic switches at said automatic exchange, means at said dialling operators switchboard for controlling the operation of said automatic switches over any one of said trunks, and means at said toll switchboard for completing a toll connection over the trunk used.

In witness whereof, I hereunto subscribe my name this 13th day of June, A. D., 1923.

JOHN WICKS. 

